The Day We Died
The Day We Died From the previous episode, Peter Bishop has stepped into the Machine to attempt to stop it after Walternate had activated the version in the Alternate Universe. He gains consciousness in the future, after an attack at the One World Trade Center. In 2026, the prime universe is suffering from the same singularities that have already destroyed the parallel universe, as a result of the two universes being inextricably linked together. Though the Fringe Division that developed in this universe have been able to use Amber to contain these vertices, a group called the "End of Dayers", led by a man named Moreau, attempts to breach the fabric of reality at soft spots and create more vertices. After one such incident at a theater, Peter and Olivia Dunham, now married, along with Astrid Farnsworth and Ella Dunham, Olivia's niece and now a rookie Fringe agent, find an unactivated container that they believe the End of Dayers used to trigger the breach. Fringe is unable to determine how the container works, and Peter convinces Phillip Broyles, now a Senator, to allow him to release his father Walter Bishop from maximum security prison to help identify its workings. After tearfully reuniting with his son and new daughter-in-law, Walter discovers the device uses a unique radioactive signature that they can track. The strongest source points to a used campground, where Peter discovers a key. He recognizes the key as from Walter's old home near Reiden Lake and travels there alone, and finds his biological father, Walternate, present. Walternate admits to being behind the End of Dayers group, as his revenge for Peter activating the Machine and destroying the parallel world that was his home. Walternate promises that Peter will face the same pain and suffering he has faced since crossing to the prime universe on a mission of mercy, one piece at a time. Peter realizes that Walternate is speaking of Olivia, and finds that the Walternate he is talking to is a hologram. Meanwhile, in Central Park, where Moreau has set off another breach to expose an existing wormhole, Olivia is helping to cordon off the breach when Walternate approaches and kills her. Peter and the rest of Fringe division struggle with her death at her funeral. Walter continues to study the Central Park wormhole and discovers that it links to the past, approximately 200 million years ago. He comes to realize a temporal paradox: he will have sent the device piece by piece into the past, effectively becoming the "First People" mythos, and convinces Peter that they can influence Peter in the past by having him experience the end of days himself and make a different decision when he enters the machine. Peter, back in 2011 in the machine, wakes up to find Olivia still alive, and himself still in the machine. In the parallel universe, Walternate attempts to convince Olivialternate to help stop the machine. Peter recalls his experiences from the future, and uses the machine to merge the rooms from both universes into one. While Olivia and Walter and their dopplegangers stare each other down, Peter convinces the two sides to work together to try to repair the damage to save both universes, then suddenly disappears. The Olivias and Walters agree that they need to put aside their differences in order to save both worlds. Outside on Liberty Island in the original universe, the Observers watch as September notes to December that Peter has already been forgotten by his friends, his purpose having been served, and concludes that Peter now never existed.